1. Technical Field
This invention relates to a system and method for locating pre-established sites behind a covering material like a wall or ceiling, and more specifically the invention provides a system and method for locating marked sites while eliminating false findings of unmarked sites.
2. Background Art
During the construction of buildings and structures, objects or bodies such as wiring, plumbing, or pest control tubes are mounted with respect to structural frame members such as wood or metal studs. After the bodies are mounted to the structural frame members, a covering material such as drywall, paneling, or plywood is placed over the structural members, concealing the objects or bodies mounted to the internal structural members. Further construction efforts, subsequent modification work, or repair efforts may require the covering material to be cut or pierced to expose the internal components.
Conventional devices and methods exist for locating and accessing a narrow class of objects such as electrical boxes. One such device, as described in U.S. Pat. No. 4,384,396, utilizes an “apparatus and method for use in installation of an electrical receptacle box and in particular for use in cutting an access opening in wallboard installed in covering relationship to the electrical receptacle box” which utilizes “first and second magnets having opposite polarity.” (abstract) Another such device, as described in U.S. Pat. No. 6,708,421, utilizes “a locating device for locating a body such as an electrical box behind a wall or ceiling” wherein magnets are utilized in order to locate the body. (abstract) Magnets, however, are attracted to a variety of items which may be located within a wall. Consequently, a system and method is needed to expand the ability to mark and locate any object, body, position, member, etc. concealed by some covering material.
Conventional systems and methods are based on the attraction of magnets to locate concealed sites. These systems tend to contemplate use of the magnets in configurations where the magnets will attract each other as a means of locating concealed sites. These conventional systems are deficient in providing a way to differentiate between a locating device being magnetically attracted to a concealed magnet or to a concealed metallic object such as a nail or metal stud.
Consequently there is a need for a system and method for utilizing the polarity of magnets as a means of locating only marked locations while eliminating false positives occurring when a locating magnet is attracted to a metallic body that behaves like a temporary magnet due to the magnetic field produced by the locating magnet.